T-Wave Oversensing with Contemporary Implantable Cardioverter-Defibrillators

Abstract

Background: Implantable cardioverter-defibrillators (ICDs) need to reliably detect ventricular tachycardia (VT) and ventricular fibrillation (VF) while avoiding T-wave oversensing (TWOS), which is associated with a risk of inappropriate therapies. The incidence of TWOS with endovascular ICDs appears to differ between manufacturers.

Objectives: We aimed to evaluate the incidence and clinical consequences of TWOS with contemporary Medtronic and Boston Scientific ICDs.

Methods: Consecutive patients implanted with a recent Medtronic or Boston Scientific ICD and remotely monitored at three French centers were included. All transmitted EGMs labelled as VF, VT, non-sustained VT (NSVT), or ventricular oversensing (Medtronic) were screened for TWOS.

Results: Among 7589 transmitted episodes from 674 patients with a Boston Scientific ICD, we did not identify a single case of TWOS. Among 16,790 transmitted episodes from 1733 patients with a Medtronic ICD, we identified 60 patients (3.4%) with at least one episode of TWOS. In 46 patients, TWOS was intermittent (NSVT episodes). In the remaining 14 patients, TWOS resulted in 60 sustained episodes (completed counters). No inappropriate therapies were delivered in 12 of these patients because no therapies were programmed (in monitor zones, 11 episodes) or because therapies were inhibited by the morphology discriminator (Wavelet, 19 episodes) or by the anti-TWOS algorithm (26 episodes). Two patients received inappropriate therapies due to TWOS (0.1% of patients with Medtronic ICDs).

Conclusion: On review of 24,379 transmitted episodes from 2407 patients with endovascular ICDs, we found no case of TWOS with Boston Scientific devices, whereas TWOS was not uncommon with Medtronic devices. However, the risk of inappropriate therapy with Medtronic ICDs was very low (0.1%) due to the often intermittent nature of this phenomenon, the morphology discriminator, and the anti-TWOS algorithm.

Keywords: T-wave; algorithm; implantable cardioverter–defibrillator; oversensing; remote monitoring.

Figure 1

Episode recorded as nsVT showing intermittent TWOS (blue squares) resulting in a “train track” pattern as the alternating R-T and T-R intervals form two separate lines. The TWOS self-terminates before detection of VT/VF is reached.

Figure 2

Episode recorded as SVT showing T-wave oversensing (blue squares) resulting in an alternating match/no match pattern. Given that at least 3 complexes match with the template, the Wavelet algorithm inhibits inappropriate therapies.

Figure 3

Episode recorded as ventricular oversensing showing TWOS (blue squares) correctly detected by the anti-TWOS algorithm. The “TW” markers (blue arrow) indicate that the anti-TWOS algorithm is active and inhibits VF/VT therapies.

Figure 4

Episode recorded as treated VF/VT showing TWOS not detected by the anti-TWOS algorithm because the criterion requiring 6 consecutive sensed events is not met and because of the presence of intermittent ventricular pacing.

Figure 5

Episode recorded as treated VF/VT showing TWOS not detected by the anti-TWOS algorithm as is it disabled by intervals ≤140 ms between sensed events (blue arrows). The Wavelet algorithm is not applied as the rhythm is faster than the SVT V limit (260 ms).